Question
Answer and Explanation
The term "make install_root" is commonly encountered when working with the make build system, particularly in the context of software compilation and installation on Unix-like operating systems (such as Linux and macOS). It refers to a variable used during the installation phase of a software build process.
Here's a breakdown of what it means:
1. `make` Build System: The make utility is a build automation tool that reads a file called Makefile, which contains instructions on how to compile and install software. These instructions often include steps for copying compiled files to their final destination.
2. Installation Process: The installation process typically involves copying executable files, libraries, configuration files, and other resources to specific directories on the system. These directories are usually located under the root directory (/), such as /usr/bin, /usr/lib, /etc, etc.
3. `install_root` Variable: The install_root variable is used to specify an alternative root directory for the installation. Instead of installing files directly under the system's root directory (/), the files are installed under the directory specified by install_root. This is particularly useful for:
- Creating Packages: When creating software packages (e.g., .deb, .rpm), the package builder needs to install files into a temporary directory before packaging them. install_root allows the build process to install files into this temporary directory without affecting the actual system.
- Testing Installations: Developers can use install_root to install software into a test directory to verify the installation process before deploying it to a production environment.
- Cross-Compilation: When cross-compiling software for a different architecture or operating system, install_root can be used to install the compiled files into a directory that mirrors the target system's file structure.
4. Usage: The install_root variable is typically used with the make install command. For example:
- make install DESTDIR=/tmp/my_install
- In this example, DESTDIR is often used as an alias for install_root. The software will be installed into the /tmp/my_install directory instead of the system's root directory.
5. How it Works: When make install is executed with install_root, the Makefile uses the specified directory as the base for all installation paths. For example, if the Makefile specifies that an executable should be installed to /usr/bin/my_program, with install_root=/tmp/my_install, the executable will be installed to /tmp/my_install/usr/bin/my_program.
In summary, "make install_root" is a mechanism to redirect the installation of software to a specified directory, which is crucial for packaging, testing, and cross-compilation scenarios. It allows developers to control where the software is installed without affecting the system's root directory.